1. Field of the Invention
The present invention relates to a laminated glass.
2. Discussion of Background
In recent years, it has been desired to reduce the weight of an automobile body to improve the gasoline mileage of the automobile. For the weight reduction, it is necessary to reduce the weights of various components constituting the automobile body, and such weight reduction is required also for a window glass. To reduce the weight of a window glass, it is necessary to either reduce the size of the glass sheet to be used or to reduce its thickness, and in order to reduce the weight without changing the design of the shape of the window glass, it is necessary to reduce the thickness of the glass sheet.
However, if the glass sheet is made thin for weight reduction, there will be a problem such that the effect for shielding solar radiation energy by the glass sheet will decrease, and the internal temperature of the automobile will increase, whereby the load for air conditioning will be excessive. The solar radiation transmittance of a glass sheet changes in the order of the second power of the thickness of the glass sheet. Accordingly, if a glass sheet is made thin even slightly, the solar radiation energy passing through the glass sheet sharply increases.
Further, by making the glass sheet thin, the sound-insulating performance of the glass sheet decreases, whereby there will be a problem that sounds outside the car will enter into the car, and the comfortableness in the car will thereby be deteriorated. Generally, a material has a nature that the higher the mass per unit area (the surface density), the higher the sound insulating ability, and the higher the frequency of the sound, the easier the insulation of the sound (mass law). Such a sound insulating ability is evaluated by a sound transmission loss TL (=10xc2x7log10(i/xcfx84)[dB], wherein xcfx84=Et/Ei, wherein Et is the energy of the sound passed through the substance, and Ei is the energy of the sound entered into the substance), and the larger the TL, the better the sound-insulating ability.
On the other hand, in a case where a substance has a flat sheet shape, it may undergo resonance phenomena at a specific frequency, whereby the sound transmission loss tends to be lower than the mass law (coincidence effects). Such a frequency at which the sound transmission loss decreases, is called a coincidence resonance frequency, and it shifts towards a high frequency side when the thickness of the glass sheet is made thin, whereby noises in a high frequency region generated outside of the car tend to enter into the car.
Thus, heretofore, making a glass sheet thin in order to reduce the weight of an automobile, has brought about two problems i.e. decrease in the infrared shielding ability and decrease in the sound insulating ability.
Accordingly, it is an object of the present invention to provide a laminated glass whereby weight reduction can be realized without lowering the infrared shielding ability and the sound insulating ability.
The present invention has been made to solve the above problems and provides a laminated glass having a surface density of at most 12 kg/m2 and comprising a plurality of glass sheets laminated one on another with an interliner provided between the respective adjacent glass sheets, wherein the interliner has an ability to shield infrared rays and an ability to insulate sounds having a frequency of 5,000 Hz.